There has long been a desire to deliver drugs intradermally. The skin comprises two layers, the outer or upper surface called the epidermis, and the internal surface referred to as the dermis. The epidermis does not contain any blood vessels and it is dependent on the underlying dermis for nutrient delivery and waste disposal via diffusion. The inner layer, the dermis, is composed of two layers, the more superficial papillary dermis and the deeper reticular dermis. The papillary dermis is thinner and consists primarily of loose connective tissue containing small capillaries, elastic fibers, reticular fibers and some collagen. The deeper reticular dermis consists of a thicker connective tissue containing larger blood vessels, interlaced elastic fibers and core spindles of collagen fibers arranged in layers parallel to the surface. The reticular layer also contains many antigen-presenting cells, fibroblasts, mast cells, nerve endings, and lymphatics. Because of the high amount of blood vessels, lymphatics and antigen presenting cells in the dermis, this is an ideal site for delivery of drugs and/or antigens.
A major problem, however, with intradermal delivery is the difficulty in precisely delivering the drug into the dermal layer. Generally, the outer layer, the epidermis, has a thickness of about 0.05 to 2 mm and the dermis has a thickness between about 1.5 and 4 mm. Thus, to deliver an agent to the dermis, the needle must penetrate the skin to a depth of no more than 5 mm, preferably between about 2 and 4 mm. It is very difficult to control an injection to this shallow depth. For certain types of injection, such as the Mantoux test for tuberculosis, a fine gauge needle is inserted at a 45° angle to try and get the agent into the dermis.
Several efforts have been made to try and find reliable ways of delivering agents to the dermis. For example, United States Patent Application No. 2005/0124967 is directed to a method for directly delivering a high molecular weight substance into an intradermal space within mammalian skin comprising administering the substance through at least one hollow needle having an outlet with an exposed height between 0 and 1 mm, said outlet being inserted into the skin to a depth of between 0.3 mm and 2 mm, such that delivery of the substance occurs at a depth between 0.3 mm and 2 mm and a microneedle for intradermal injection of a high molecular weight pharmaceutical substance, wherein the microneedle has a length and outlet selected for its suitability for specifically delivering the substance into the dermis.
U.S. Pat. No. 5,527,288 discloses an intradermal drug delivery device for delivering a liquid drug to a subject via the subject's skin, comprising a housing having a lower surface for application to the skin of the subject; means for affixing the housing in position with the lower surface in contact with the subject's skin; and a drug reservoir within the housing. The reservoir is in the form of an expansible-contractible chamber which is expanded when filled with the drug and which can be contracted to dispense the drug therefrom. A single hollow needle is associated with the drug reservoir and extends through the lower surface, having an inner end communicating with the drug reservoir and an outer end projecting outwards a sufficient distance so as to penetrate through the epidermis and into the dermis when the housing is pressed against the skin. The device also includes means for actively discharging the drug from the reservoir to the subject's skin via the needle.
U.S. Pat. No. 6,689,118 is directed to a method of making an intradermal injection into the skin of an animal to obtain systemic delivery or to induce an immune response. The method comprises providing a drug delivery device including a needle cannula having a forward needle tip and a needle cannula being in fluid communication with a substance contained in said drug delivery device; inserting the needle tip into the skin of an animal and engaging the surface of the skin with a skin engaging surface of a limiter portion such that the skin engaging surface of the limiter portion limits penetration of the needle tip into the dermis layer of the skin of the animal; and expelling the substance from the drug deliver device through the needle tip into the skin of the animal to expose the injected substance to the microcirculatory blood vasculature and the lymphatic plexuses.
U.S. Pat. No. 6,569,143 is directed to another related method of making an intradermal injection comprising providing a drug delivery device; inserting a needle tip into the skin of an animal whereby penetration of the needle tip is limited to the dermis layer of the skin of the animal; and expelling the substance from said drug delivery device through the needle tip into the skin of the animal.
U.S. Pat. No. 5,997,501 describes an intradermal drug delivery device for the delivery of at least one drug to a subject via the subject's skin. The device comprises a housing having a lower surface; a drug reservoir located with the housing; a cover that is adjustable engaged with the housing from a first extended position to a second retracted position such that the cover is proximal to the lower surface of the housing when the cover is retracted and the cover is distal to the lower surface of the housing when the cover is extended; means for affixing the cover in position with the lower surface of the housing in contact with the subject's skin; a single hollow needle fixed to the cover and having a first end in communication with the drug reservoir and a second end projecting outwards no further than the lower surface of the housing when the cover is extended, and to penetrate through the epidermis and into the dermis when the cover is retracted; and means for actively discharging the drug from the reservoir to the subject's skin via the needle.
Although multiple efforts have been made to try and provide a device for intradermal delivery, many of the prior art devices are expensive to manufacture or can only be used for one drug. In spite of all the efforts made to provide a method and/or device for intradermal delivery, there remained a need for a reliable, single-use, disposable device for intradermal delivery.